1. Field of the Invention
The invention relates to the field of clamps. More particularly, the invention relates to the adaptation of spring clamps for use as edge clamps.
2. Description of the Prior Art
The hand spring clamp is a common tool for cabinetmakers and others who work with wood. It is rugged, inexpensive, readily available in hardware and other stores that sell tools, and available in a range of sizes. Most cabinetmakers have an assortment of these clamps, in various sizes. A typical example of such spring clamps is the PONY(copyright) clamp. These are simple tools comprising two lever arms pivotally connected to one another, with a sturdy coil spring located at the pivot point for urging the jaw ends of the clamp to close against each other. The clamps are without extraneous parts that can be misplaced or fall off, do not require adjusting to the thickness of the workpiece being clamped, and require only one hand to operate them, leaving the other hand free to hold the workpiece in position.
The conventional spring clamp is limited to applications in which clamping force is required only in a direction that is perpendicular to the longitudinal axis of the clamp. Many situations in woodworking, however, require the application of a clamping force in a direction coaxial with the longitudinal direction of the clamp. For example, the jaws of a spring clamp provide a clamping force against the upper and lower surfaces of a board, but do not provide a clamping force against the edge of the board, that is, against the surface of the board between the upper and lower surfaces. Either three-way C-clamps or long-bar or pipe clamps are typically used to provide this edge-clamping action. Both of these types of clamps have disadvantages in that they are time-consuming and tedious to use because they require that be properly tightened to provide the desired clamping action. Not only does manipulating the adjusting mechanism take time, but it also requires the use of both hands. Bar or pipe clamps also require access to opposite sides of the board to which edging is being applied.
Over the years, several attempts have been made to adapt the conventional hand spring clamp for use as an edge clamp. One such attempt is disclosed by U.S. Pat. No. 5,765,820 (Marusiak; issued 1998), which teaches the insertion of a flat spring into the conventional spring clamp. As the biasing spring forces the jaw ends of the clamp closed, the flat spring is forced into a curved shape that projects forward between the two jaws. This flat spring effectively applies a compressive force against the perpendicular edge of the horizontal surface being clamped by the spring clamp. The disadvantage of the Marusiak device is that, to be reliable and effective, the flat spring may have to be fastened within the clamp. This can be done by providing some type of riveted fastening, or a snap-fit mechanism formed by a protrusion on one part and a receiving hole or aperture on the other part. Once modified, the spring clamp is readily usable as an edge clamp, although it involves a certain amount of time and work to achieve the needed modification.
Other attempts have been made to adapt the spring clamp by permanently or semi-permanently mounting an edge-clamping mechanism onto the spring clamp. Generally, the clamping adaptations extend into the space between the jaw ends, thereby reducing the effective depth of the jaw. Such modified spring clamps are disclosed by U.S. Pat. Nos. 6,161,823 and 5,863,033, both issued to Bradford, in 2000 and 1999, respectively. Because the modification is permanent or semi-permanent, the cabinetmaker is required to have twice the number of normally required spring clamps, one set for use as the conventional spring clamps, a second set for use as edge clamps.
What is needed therefore is a quick and reliable method of and device for adapting a spring clamp for use as an edge clamp. What is further needed is such an adaptation that can also be quickly and easily removed so that the spring clamp may be returned to its conventional use. What is still further needed is such an adaptation that allows full use of the depth of the jaw cavity of the clamp.
It is an object of the present invention to provide a device for modifying a conventional spring clamp for use as an edge clamp. It is a further object to provide such a device that is easily mounted and easily removed from the spring clamp. It is a yet further object to provide such a device that does not require any preparatory work on the spring clamp. It is a still further object to provide such a device that allows the clamp to be used to its full jaw cavity depth. An finally, it is an object to provide such a device that is inexpensive and increases the economic efficiency of the conventional spring clamp.
The objects are achieved by providing an edge-clamp adapter that slips over the jaw ends of the conventional spring clamp and provides a clamping action between the jaw ends in a direction coaxial with the longitudinal direction of the spring clamp and perpendicular to the clamping action of the jaw ends.
The edge-clamp adapter comprises essentially a flexible strip of material that is removably attached to the jaw ends of a hand spring clamp such that, when the spring clamp is opened, the flexible strip of material extends between the jaw ends across the clamp cavity. As the spring clamp is then applied to a workpiece to be clamped, the flexible material of the edge-clamp adapter fits or wraps around the contour of the workpiece, thereby providing a compressive force against the edge face of the workpiece that is between the surfaces gripped by the jaw ends of the clamp.
The edge-clamp adapter can be made of a variety of materials that are elastic or inelastic. The term xe2x80x9celastic materialxe2x80x9d is used herein to designate a material that is repeatably stretchable a distance that is at least a substantial portion of the length of the material and that rebounds substantially to its original dimensions. Suitable elastic materials include latex, gum rubber, neoprene, and other elastic materials, particularly those with good abrasion and tear resistance properties. Ideally, the elastic material has sufficient stretchability so that when the spring clamp is clamped about a workpiece that extends deep into the jaw cavity of the spring clamp, the elongation properties of the elastic material allow the clamp adapter to stretch around the workpiece without reaching its elastic limit.
The clamp adapter can be made entirely of elastic material, for example, or can have ends of a nonelastic or slightly elastic material that slip over or attach to the jaw ends by some fastening means, and an intermediate section of highly elastic material connecting the ends. The fastening means can include pockets that slip over the jaw ends, or a hook-and-loop type fasteners, wherein one part of the fastener is attached to the jaw ends and the mating part is attached to the ends of the clamp adapter. The possibilities for attaching the clamp adapter to the hand spring clamp are myriad. As long as those means are easily attachable to and easily removable from the hand spring clamp, and yet securely hold the clamp adapter in proper position on the clamp, they are suitable and are included within the scope of the present invention. The clamp adapter can also be made of a substantially inelastic material such as webbing. Because of the energy stored in a stretched elastic material, however, elastic material provides a greater and a more reliable clamping force than inelastic material and also provides greater adaptability to clamping needs. The description of the present invention will hereinafter refer to an elastic clamp adapter, although it is understood that a non-elastic clamp adapter is also included within the scope of the invention.